The present invention pertains to a hemming device according to the preamble of patent claims 1 and 2.
xe2x80x9cHemmingxe2x80x9d is defined as the positive-locking connection of two parts by folding over a flange. Especially an outer sheet metal and an inner sheet metal are connected to one another hereby in the manufacture of vehicle bodies.
For example, the following systems are available for the hemming of body parts:
1. Hemming tools which are used in presses and perform the prehemming or finishing hemming of the flange by a vertical movement of the upper part of the tool. Such a hemming process has been known from DE 44 18 684 A1, where a slide moves radially inwardly and subsequently again radially outwardly for the prehemming and a second hemming tool is displaced vertically by means of the press punch for the finishing hemming. Special efforts are needed for feeding and removing the components due to the arrangement of the press above the folding bed. Above all, the upper tool must perform a long stroke.
2. Hemming devices in which the hemming bed is stationary and the flange to be hemmed is bent over by hydraulically or electrically operated slides or mechanical rocker arm elements. The actuation and operation of the hemming slides and the rocker arm element are complicated (cf. DE 197 47 292 C1).
3. A hemming device of this class has been known from U.S. Pat. No. 5,150,508, in which the lower folding bed, on which the sheet metals to be connected are placed, performs a separate hemming stroke for the prehemming and the finishing hemming and presses in the process the flange to be folded one after another against the stationary prefolding jaws and finishing folding jaws. The prefolding and finishing folding jaws are arranged rigidly on a horizontally displaceable slide. The folding bed must be displaced vertically and the folding jaws horizontally for the prefolding and the finishing folding. The folding bed must then perform a long displacement travel between the prefolding operation and the finishing folding operation and the hemming stroke proper in the particular positions.
The basic object of the present invention is to propose a device of this class, in which the vertical movement of the folding bed is limited to a minimum and the prefolding and finishing folding jaws are brought into position by secure and simple movements.
To accomplish this object, it is proposed that the prefolding jaw is also displaceable from the outside to the inside into the prehemming position by means of a slide and relative to the slide of the finishing folding jaw.
As an alternative to the displaceability of the prefolding jaw, it is proposed according to the present invention that the prefolding jaw is fastened to a pivoting plate and can be pivoted from the outside to the inside into the prehemming position by actuating the pivoting plate, and that the pivoting plate can be locked with the prefolding jaw fastened to it in the prehemming position. Meaningful embodiments for this are shown in the subclaims 3 through 10.
Due to the fact that the folding jaws can be displaced according to the present invention on slides of their own possibly independently from one another into the hemming position above the folding bed for the prefolding and the finishing folding, the displacement travel of the folding bed can be considerably reduced. The prefolding and finishing folding jaws can be brought one after another into the same hemming position especially if the guide paths of the two slides are arranged at acute angles in relation to one another, so that a long adjustment movement of the folding bed between the prefolding and the finishing folding is not necessary. Consequently, the folding bed performs only the hemming stroke proper each time for the prefolding and the finishing folding, and this hemming stroke takes place at one and the same point. The same is also possible in the alternative embodiment, the combination of the pivotable prefolding jaw with the displaceable to finishing folding jaw.
It proved to be favorable to arrange the slide for prefolding or the pivoting plate on the slide for finishing folding or vice versa. In this so-called piggyback arrangement or slide-on-slide arrangement, the displacement travels for the individual slides are limited to a minimum. In addition, an especially compact design is possible. A spring actuated holding-down device, which fixes the two sheet metals on the surface of the folding bed already before the beginning of the prefolding and finishing holding operation, may be arranged on the upper slide, preferably the slide for the prefolding or on the pivoting plate.
It proved to be favorable in the alternative embodiment according to the present invention to mount the drives for the slide with the finishing folding jaw and the pivoting plate on a common bracket in an articulated manner, wherein the bracket itself is rigidly connected to the base. Moreover, the pivoting plate may be mounted on another bracket, which is likewise rigidly connected to the base or to the slide, in a rotatingly movable manner via an additional hinge.
The pivoting plate can be locked in the working position by a locking unit, which is brought into the locked position by a movement of the slide for the finishing folding with the existing drive unit being arranged on the slide for the finishing folding. However, the pivoting plate and the slide may also be coupled with one another such that the prefolding and finishing folding jaws can be forcibly moved one after another into the working position with a common drive unit. It proved to be favorable in this connection to arrange stops at the pivoting plate and the slide, which are brought into contact for locking the prefolding jaws. The pivoting plate can then be pivoted upwards by means of a connecting link guide present at the slide for the subsequent finishing folding. Only one drive unit is necessary here for the linear movement of the slide, because the pivoting plate is inevitably also actuated at the same time with the movement of the slide.